1. Field of the Invention
The present invention relates to a wet type electrophotographic printer, and more particularly, to a developer liquid supply device of a wet type electrophotographic printer, in which the developer concentration and liquid level can be controlled.
2. Description of the Related Art
In general, a wet type electrophotographic printer prints a desired image by developing an electrostatic latent image formed on a photosensitive medium such as a photosensitive belt, with a predetermined color developer liquid, and transfers the developed image to a paper sheet. The wet type electrophotographic printer is provided with a developing unit, for supplying the developer liquid to the photosensitive medium, and a developer liquid supply device, for continuously supplying the developer liquid of a predetermined concentration to the developing unit. The developer liquid is a mixture of concentrated ink, containing a powder toner, and a liquid carrier. The concentration of the toner is about 2-4 wt %. Hereinafter, the concentration of the developer liquid is defined by the wt % of the toner.
The developer liquid supply device is provided with an ink cartridge for storing the concentrated ink, a carrier cartridge for storing the liquid carrier, and a reservoir for storing the developer liquid which is a mixture of the concentrated ink and the liquid carrier at a predetermined ratio. In addition, in the ink cartridge and the reservoir, agitators may be installed so the toner contained in the stored liquid does not precipitate.
In the developing device having the structure described above, since the developer liquid stored in the reservoir is decreased by the amount used in developing each electrostatic latent image of the photosensitive medium, the concentrated ink and the liquid carrier must be continually supplied to the reservoir in order to maintain the developer liquid at a constant concentration. In addition, it is necessary to maintain the level of the developer liquid stored in the reservoir at a specified height.
Further, the respective consumptions of the toner and the liquid carrier may vary with images to be printed. That is, when a simple image or a small image is printed, more liquid carrier is consumed than toner, and when a complicated image is printed, relatively more toner is consumed than liquid carrier. Therefore, in order to maintain the predetermined concentration of the developer liquid, it is necessary to appropriately supply the toner and the developer liquid to the reservoir in accordance with the respective consumptions of the toner and the liquid carrier.
However, with the above developer liquid supply device, the concentration and level of the developer liquid cannot be successfully adjusted at the same time. That is, when a large amount of the liquid carrier is supplied to the reservoir in order to maintain the constant concentration of the developer liquid in the reservoir, the level of the developer liquid may become inappropriate for printing, or when the level of the developer liquid is adjusted, the correct concentration of the developer liquid may be lost.